EXPLOSION IN TURRET TWO
Investigation Continued

e.   "Too tight liner”:  This idea originated in the ship, apparently on the basis of bore erosion gage readings taken after some tens of shots fired since the most recent relining.  The readings were less than the nominal for a new liner (actual readings not having been taken before firings with the new liners), and were thought possibly to indicate a smaller than normal bore diameter at the rifling origin.  Such a decrease in gage readings (“negative erosion”) with initial firings has long been known, and denotes no abnormalities.  It has been ascribed to a mandrelling action of the projectiles in the liner, which initially displaces the rifling origin longitudinally somewhat to the rear, rather than to any change in radial dimensions.  Further, post-casualty star-gaging of the guns in the undamaged turrets revealed no dimensional abnormalities, and there is no reason to believe these differed from the casualty gun.

f.    "Oversize projectiles”  This thought also originated in the ship, apparently on the basis of a projectile received in a recent replenishment, judged abnormal by visual inspection (for reasons not recorded and no longer retrievable), and returned to the issuing unit.  The diameter gaging included in the re-certification results reported in reference (j) lists 46 projectiles that would not pass the bourrelet “go” gage, a cylindrical gage ring of specified internal diameter.  But all of these failures appear to be attributed to one or more local oversize areas at the bourrelet, including scars or burrs, which we do not believe would have discernable effects in either loading or firing.  In any case, proving ground experience indicates that projectiles with some degree of excess diameter at the bourrelet (point of largest diameter) can be fired without apparent harmful effects: if the relatively low-powered rammer can load the projectile fully into the bore, the propellant charge will move it out the muzzle without further ado.

g.   Steel constriction of the bore:  This form of bore obstruction has been encountered in the past with some guns, caused by the mandrelling action of the projectiles tending to elongate the liner forward so it rides over a liner shoulder.  The post-casualty star-gaging noted in paragraph e. above found no such constriction in the guns of the undamaged turrets, and there is no reason to believe there was one in the casualty gun.  In any case, we now know the projectile detonated at a position in the bore such that its bourrelet was some 8” short of the only shoulder that could have caused such a condition.

Technical Control of Gun Ammunition

42.       We are concerned over the control of technical features of Navy gun ammunition, particularly as regards ammunition safety for fleet users.  Preceding paragraphs have noted the serous degradations which began to show up in the fleet, commencing in 1965.  The correlation appears inescapable between them and the organizational changes which had begun not long before, and which bear upon command management and control of gun ammunition technical matters.